Morris Minor Owners Club

Hi,

I have a 1970 4-door saloon with a dynamo and the ignition light tends to come on slightly and intermittently when the engine is idling. Is this normal behaviour? The idling rev speed is normal, not too low.

Yes, perfectly normal, with an engine in good condition it should be possible to set the tickover to a reliably slow speed which would allow the ignition warning light to glimmer. If it is glimmering then the dynamo is not charging.

What's it mean if the ignition light is on all the time, but the dynamo appears to be charging fine? Where's the fault? That's one of the little nigglers I have...

My red light is on all the time as well.I have reconditioned , tested and fitted another dynamo , tried another regulator box , checked and double checked all connections and still the f-----g light comes on.Does anyone have any idea what it could be ?

Hello all,

usually if the light is on all the time then the dynamo or alternator is not charging. If you are certain that it is charging, then a wiring fault must be the reason.
The ignition light is fed from the ignition switch (battery voltage) and is connected to the regulator. This regulator connection goes to earth which is why the light is bright when you first switch on, when starting, normally generated voltage from the regulator means no voltage (very little actually) across the bulb and it goes out. I.E., it does not have an earth connection except through the generator/regulator circuit.
I think I would look at the bulbholder or regulator connections in case they have been messed with. I can't think of any other reason as a short circuit to earth would be very obvious.

Alec

Hi
Sorted my red light problem.Bought and fitted a new regulator box from ESM.Light went off on starting.Old box looked as clean as a whistle but it obviously was faulty.

Yep - as Alec has detailed -the light can only glow when there is a voltage difference across it - between battery and generator. So if it's ON the generator is not generating!